1. Field of the Invention
The present invention relates to a liquid-jet head for ejecting liquid droplets and to a method for manufacturing the liquid-jet head, as well as to a liquid-jet apparatus comprising the liquid-jet head. More particularly, the invention relates to an ink-jet recording head in which a vibration plate partially constitutes pressure generating chambers communicating with corresponding nozzle orifices, piezoelectric elements are formed on the surface of the vibration plate, and deflection of the piezoelectric elements causes eject of ink, and to a method for manufacturing the ink-jet recording head, as well as to an ink-jet recording apparatus comprising the ink-jet recording head.
2. Description of the Related Art
Ink-jet recording heads which have been put into practical use include two kinds in which a vibration plate partially constitutes pressure generating chambers communicating with corresponding nozzle orifices for ejecting ink droplets, and piezoelectric elements cause the vibration plate to be deformed so as to apply pressure to ink contained in the corresponding pressure generating chambers to thereby eject ink droplets from corresponding nozzle orifices. One such kind of ink-jet recording head uses piezoelectric actuators that operate in the longitudinal vibration mode; i.e., piezoelectric actuators that extend and contract in the axial direction of the piezoelectric elements. The other kind of ink-jet recording head uses piezoelectric actuators that operate in the flexural vibration mode.
A known ink-jet recording head using piezoelectric actuators that operate in the flexural vibration mode is manufactured, for example, in such a manner that a piezoelectric layer is uniformly formed on the entire surface of a vibration plate by film forming technique; and the piezoelectric layer is lithographically divided into portions corresponding to pressure generating chambers, thereby forming independent piezoelectric elements corresponding to the pressure generating chambers.
An ink-jet recording head using such piezoelectric elements has a structure in which lower electrodes of the corresponding piezoelectric elements are patterned so as to correspond to pressure generating chambers to thereby suppress initial deflection of a vibration plate, thereby increasing working deflection of the vibration plate effected by actuation of a piezoelectric element (refer to, for example, Japanese Patent Application Laid-Open (kokai) No. 2000-326503 (FIG. 7)).
However, formation of a piezoelectric layer on the patterned lower electrodes results in poor film quality of a portion of the piezoelectric layer that overlies the vibration plate and end portions of the lower electrodes, resulting in low reliability of driving performance. Specifically, a portion of the piezoelectric layer overlying the lower electrodes differs in properties such as crystallinity from a portion of the piezoelectric layer overlying the vibration plate. As a result, the piezoelectric layer becomes substantially discontinuous in a region in the vicinity of the end portions of the lower electrodes. When voltage is applied to the piezoelectric layer, such discontinuity causes occurrence of fracture, such as cracking, of the piezoelectric layer. Particularly, the piezoelectric layer tends to be fractured in a region corresponding to longitudinal end portions of the lower electrodes. Such a problem arises in not only ink-jet recording heads that eject ink, but also liquid-jet heads that eject droplets of liquid other than ink.